In a large bowl, combine the plums, brown sugar, 3 tablespoons flour and cinnamon. Spoon into a greased 2-qt. baking dish. , In a small bowl, combine the sugar, baking powder, salt, mace and remaining flour. Add egg; stir with a fork until crumbly. Sprinkle over plum mixture. Drizzle with butter. , Bake at 375° for 40-45 minutes or until plums are tender and top is golden brown. Cool for 10 minutes before serving. Serve warm or at room temperature.